Fibroblastic cells isolated from scleroderma skin and rheumatoid arthritis synovial tissue display abnormal metabolic phenotypes that play a role in disease pathogenesis. Furthermore, the metabolic alterations are persistent for many cell generations of in vitro culture. We propose to use in vitro models to investigate mechanisms whereby products of immune cells may lead to permanent phenotypic changes in connective tissue cell populations. We will utilize fibroblast substrains we have isolated which are heterogeneous in metabolic activity to study whether immune mediators might lead to preferential growth of certain subpopulations, i.e. clonal selection, and the possible mechanisms involved. The phenotypic distribution of fibroblast substrains isolated from scleroderma skin and rheumatoids synovium will be compared to that seen in normal controls. Synthesis of prostaglandin E2, collagen, collagenase and glycosaminoglycans, and message levels for alpha1(I), alpha2(I) and alpha1(III) collagen will be assayed as well as biosynthetic responses to interleukin-1, gamma interferon, and other mediators. Clonal distribution of collagen mRNA will also be examined by in situ hybridization. Finally, we will continue preliminary studies using monoclonal antibodies that may identify specific fibroblast subpopulations to study the clonal distribution of fibroblasts in in vitro experiments and in cells isolated from scleroderma skin and rheumatoid synovium.